Tinting bath for photographic paper



United 2,865,746 TINTING BATH FOR PHOTOGRAPHIC PAPER Roy 'C. Bloom and Henry J. Fassbentler, Rochester,

N. Y., assignors to Eastman Kodak Company, Roch -1- ester, N. Y., a corporation of New Jersey No Drawing. Application April 5, 1956 Serial No. 576,247 2 Claims. (Cl. 96-48) been manufactured for amateur and commercial use de pending upon the preference of those making photographic prints and consequently a wide range of papers was required to be manufactured and carried by the photographic dealers. This involves considerable expense on the part of the manufacturer who must change his manufacturing process in order to produce these various tints in paper and who must carry a large inventory to meet expected customer demands.

In order to prepare suitable tints on photographic paper, there has been desired to have a solution of dye of some sort which could be used by the photographic processor in order to tint his own paper and avoid necessity for stocking as large a number in variety of tint papers. However, a suitable tintin'g material would have to be free from toxicity, be neutral in its effect on the paper, be inexpensive, be subject to fairly close reproduction in tint, and be harmless to the photographic image.

One object of this invention is to provide a one solution bath for producing cream, old ivory or buff tints in white photographic papers, after being processed. Another object is to provide a process for tinting photographic paper to provide cream, old ivory or bull tints.

We have discovered that a lignin derivative may be used to tint photographic papers. This material is the sodium salt of sulfonated lignin. Lignin can be obtained by treating wood with sodium bisulfite and sulfurous acid (sulfite process). Lignin has been identified as a natural polymeric substance partly characterized as to structural parts but known to contain aromatic rings bearing methoxyl groups (CH The sodium salt is obtained commercially as a solid material which can be dissolved readily in water. The preparation of this material is described in U. S. Patent No. 2,491,832 issued to Salvesen et al. We have found that a small amount of sodium carbonate, sodium metaborate or the like may be added to the solution to control the alkalinity. Our preferred solution contains about 8% of the sodium salt of sulfonated lignin and about 0.7% sodium carbonate.

The photographic print following normal processing is washed after it has been fixed in the sodium thiosulfate fixing bath or similar fixing solution, washed to remove the acid of the fixing solution and then immersed in the tinting bath. Depending upon the time of immersion, concentration of the bath, exhaustion and the like, the intensity of the tint may be controlled by the operator. For instance, with four grams per liter and a 60 second immersion in the bath, a very pleasing light ivory tint can be obtained. Increasing the concentration to 8 grams per liter gives a bull tone with a 60 second immersion in the bath. We have found .that the proportions range from about 2 grams per liter to 10 grams per liter for general use, but lower concentrations and higher concentrations may be used with appropriate adjustments made with the time of immersion.

The following examples indicate the method of operation of our invention but are not intended to limit its scope.

tates Patent 0 Example I Photographic prints after normal processing were thoroughly washedand then immersed in a tinting bath comprising 8.0 grams of the sodium salt of sulfonated lignin dissolved in a liter of water containing 0.71 gram sodium carbonate (Na CO3), for seconds. Theresulting tint imparted into the paper base was buff.

Example II Photographic prints after normal processing were thoroughly washed and then immersed in a tinting bath comprising 2 grams of the sodium salt of sulfonated lignin dissolved in a liter of water containing 0.71 gram sodium carbonate (Na cO for 60 seconds. The resulting tint was light ivory.

Example III Photographic prints after normal processing were thoroughly washed and then immersed in a tinting bath comprising 8.0 grams of the sodium salt of sulfonated lignin dissolved in a liter of water containing 12.5 grams of sodium metaborate for 60 seconds. The resulting tint imparted to the paper was bulf.

Example V Photographic prints after normal processing were thoroughly washed and then immersed in a tinting bath ccmprising 8.0 grams of the sodium salt of sulfonated lignin dissolved in a liter of water containing 25 grams of sodium metaborate for 60 seconds. The resulting tint imparted into the paper was buif.

Variations may be obtained depending upon the porosity of the paper inasmuch as some papers will soak up more of the tinting bath than others. However, the reproducing ability of this bath relating to a single type of paper is good and given tint can be duplicated with respect to that particular paper. Our invention may also be used with continuous processing equipment such as that used by commercial photofinishers.

The tints produced according to our invention have good stability to light and have no elfect on the photographic stability of the image.

An alternative method of applying our invention is to add the sodium salt of the sulfonated lignin to the developer to produce the desired tint and satisfactory results may be obtained. However, our preferred method is to use prints which have been washed following the fixing step.

We claim:

1. A photographic tinting bath for photographic paper consisting essentially of 2-4 parts by weight of the sodium salt of sulfonated lignin, 0.71 part by Weight sodium carbonate and 1,000 parts by weight of water.

2. A photographic tinting bath for photographic paper consisting essentially of 8 parts by weight of the sodium salt of sulfonated lignin 12.5 parts by weight of sodium metaborate and 1,000 parts by Weight of water.

References Cited in the file of this patent UNITED STATES PATENTS 2,186,717 Eggert et al. Ian. 9, 1940 FOREIGN PATENTS 442,522 Great Britain Feb. 3, 1936 

1. A PHOTOGRAPHIC TINTING BATH FOR PHOTOGRAPHIC PAPER CONSISTING ESSENTIALLY OF 2-4 PARTS BY WEIGHT OF THE SODIUM SALT OF SULFONATED LIGNIN, 0.71 PART BY WEIGHT SODIUM CARBONATE AND 1,000 PARTS BY WEIGHT OF WATER. 